gh-114545: [Lib/tempfile.py] mkdtemp - canonicalise directory name

[SamuelMarks]

On macOS—and probably other operating systems—the temporary directory /tmp is not canonical. This causes weird issues in ones codebase, e.g., /var/folders != /private/var/folders. This additional function call solves the problem.

PS: I'm not sure if the os.path.abspath call can be removed…

PPS: See #114545 for discussion; also see nodejs/node/issues/11422 for when this was discussed for Node.js.

• Issue: [cpython/Lib/tempfile.py] mkdtemp - canonicalise directory name #114545

[aisk]

I found a strange thing. After this change, the test_tempfile failed on my machine:

./python.exe -m test test_tempfile -m test_basic
Using random seed: 967898022
Raised RLIMIT_NOFILE: 256 -> 1024
0:00:00 load avg: 2.25 Run 1 test sequentially
0:00:00 load avg: 2.25 [1/1] test_tempfile
test test_tempfile failed -- Traceback (most recent call last):
  File "/Users/xxxxx/Codes/cpython/Lib/test/test_tempfile.py", line 747, in test_basic
    os.rmdir(self.do_create())
             ~~~~~~~~~~~~~~^^
  File "/Users/xxxxx/Codes/cpython/Lib/test/test_tempfile.py", line 739, in do_create
    self.nameCheck(name, dir, pre, suf)
    ~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^
  File "/Users/xxxxx/Codes/cpython/Lib/test/test_tempfile.py", line 122, in nameCheck
    self.assertEqual(os.path.abspath(ndir), os.path.abspath(dir),
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
                     "file %r not in directory %r" % (name, dir))
                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: '/private/var/folders/f3/y148281n5m73g6npw8l12lnw0000gn/T' != '/var/folders/f3/y148281n5m73g6npw8l12lnw0000gn/T'
- /private/var/folders/f3/y148281n5m73g6npw8l12lnw0000gn/T
? --------
+ /var/folders/f3/y148281n5m73g6npw8l12lnw0000gn/T
 : file '/private/var/folders/f3/y148281n5m73g6npw8l12lnw0000gn/T/eu7jqves' not in directory '/var/folders/f3/y148281n5m73g6npw8l12lnw0000gn/T'

test_tempfile failed (1 failure)

== Tests result: FAILURE ==

1 test failed:
    test_tempfile

Total duration: 338 ms
Total tests: run=7 (filtered) failures=1
Total test files: run=1/1 (filtered) failed=1
Result: FAILURE

I see that the nameCheck

cpython/Lib/test/test_tempfile.py

Line 99 in c87233f

def nameCheck(self, name, dir, pre, suf):

checks if the result of tempfile.mkdtemp is in the temp directory, which is determined by tempfile.gettempdir.

On my machine, the result of tempfile.gettempdir is not canonicalized (without the /private prefix), so the check fails. But I don't know why it passed on CI.

I'm using a Intel mac with OS version 12.7.3.

[aisk]

The test_basic passed after latest change, but there are two tests still failed:

======================================================================
FAIL: test_same_thing (test.test_tempfile.TestGetTempDir.test_same_thing)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/xxxxx/Codes/cpython/Lib/test/test_tempfile.py", line 606, in test_same_thing
    self.assertTrue(a is b)
    ~~~~~~~~~~~~~~~^^^^^^^^
AssertionError: False is not true

======================================================================
FAIL: test_basic_with_bytes_names (test.test_tempfile.TestMkdtemp.test_basic_with_bytes_names)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/xxxxx/Codes/cpython/Lib/test/test_tempfile.py", line 756, in test_basic_with_bytes_names
    os.rmdir(self.do_create(dir=d))
             ~~~~~~~~~~~~~~^^^^^^^
  File "/Users/xxxxx/Codes/cpython/Lib/test/test_tempfile.py", line 739, in do_create
    self.nameCheck(name, dir, pre, suf)
    ~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^
  File "/Users/xxxxx/Codes/cpython/Lib/test/test_tempfile.py", line 122, in nameCheck
    self.assertEqual(os.path.abspath(ndir), os.path.abspath(dir),
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
                     "file %r not in directory %r" % (name, dir))
                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: b'/private/var/folders/f3/y148281n5m73g6npw8l12lnw0000gn/T' != b'/var/folders/f3/y148281n5m73g6npw8l12lnw0000gn/T' : file b'/private/var/folders/f3/y148281n5m73g6npw8l12lnw0000gn/T/_rzdrbad' not in directory b'/var/folders/f3/y148281n5m73g6npw8l12lnw0000gn/T'

----------------------------------------------------------------------

The macOS CI failed with the same error as the previous run, despite appearing unrelated to the change. However, I suspect that a connection might not be easily detectable.

[erlend-aasland]

Marking this as draft, as it is work in progress.

[SamuelMarks]

Oh interesting; this just hit #93852